It is well known in vehicle seat belt systems to employ a guide ring through which the restraint belt is slidable. In some seat belt systems guide rings are mounted on the "B" pillar of the vehicle body to anchor the shoulder belt so that one end is routed diagonally across the occupant chest and the other end feeds into a retractor mounted on the pillar. In continuous-loop three-point belt systems having a single loop of belt, the guide ring is movable along the continuous-loop belt to define lap and shoulder belt portions of varying length. It is also known in passive belt systems to mount a guide ring on a carriage movable fore and aft along the roof rail or along the window frame of the door to permit sliding movement of the belt during movement of the belt between the occupant restraint position and a stored position permitting occupant ingress and egress.
It is desirable that the guide ring used in the above-described seat belt systems accommodate a certain range of variation in the angle of belt entry and departure relative the guide ring and that the belt be slidable longitudinally through the guide ring without folding over upon itself or twisting or binding in the guide ring.
It is well known in the prior art to mount the guide ring for pivotal movement so that the guide ring can seek a rotary position best adapted to accommodate the angular variation of belt entry and departure relative the guide ring. Scholz et al U.S. Pat. No. 4,142,274 and Lindblad U.S. Pat. No. 4,023,594 teach the provision of an auxiliary guide structure associated with the guide ring for guiding the entry or exit of the belt into the guide ring. Patents such as Scholz U.S. Pat. No. 4,142,274 and Fisher U.S. Pat. No. 3,959,855 teach that the dimension of the belt slot in the guide ring should be less than twice the belt thickness to prevent the belt from folding over upon itself.